The long-term objectives of this project are to investigate the mechanisms by which resistance to apoptosis contributes to tumor metastasis. Most epithelial cells undergo apoptotic cell death following detachment from extracellular matrix. Tumor cells can escape this apoptosis, contributing to their metastatic potential. Since more than 90% of human malignant tumors develop from epithelial cells, investigating the mechanisms of growth control in this cell type is important to the understanding and treatment of cancer. Epithelial growth control can be regulated directly by the actin cytoskeleton, and direct disruption of actin leads to apoptosis in normal cells, but not tumor cells. [unreadable] [unreadable] The first specific aim characterizes identified mutations that confer resistance to actin-dependent cell death. The second specific aim uses a transgenic mouse model to address whether apoptotic escape can enhance the metastatic potential of a known breast tumor model. The third specific aim uses a candidate approach to examine the mechanism by which the death-associated protein kinase (DAPK) is involved in actin-dependent apoptosis. This focuses on the apoptosis-induced nuclear translocation of a novel identified in vitro substrate of DAPK, Y-box-1 (YB-1) which is a known regulator of p53. [unreadable] [unreadable] Overall, the proteins and signaling mechanisms identified in each specific aim may provide new targets for therapies aimed at preventing metastasis. The immediate career goals of the candidate are to supplement prior broad experience in cellular signal transduction and genome-scale screens with training in the use of animal models of breast cancer. Philip Leder has been selected as the sponsor of this training due to his extensive experience in this area, and the substantial intellectual and technological resources available at the Harvard Medical School. The proposed studies can be freely transferred, providing a foundation for the career goal of establishing a position as an independent investigator. The proposed animal model, in combination with the results of the completed genome-scale screens should provide a suitable niche for this research focused on the molecular mechanisms by which metastatic breast tumor cells escape from actin-dependent apoptosis. [unreadable] [unreadable]